Glass grinding apparatus



Y 1934' F. B. WALDRON GLASS GRINDING APPARATUS Filed Sept. 21, 1933fi'c'deric iarhes [vi draw 1 W A var/rays Patented May 1, 1934 1,956,781GLASS GRINDING APPARATUS Frederic Barnes Waldron, Prescot, England, as-

signor to Pilkington Brothers Limited, Liverpool, England, a company ofEngland Application September 21, 1933, Serial No. 690,449 In GreatBritain September 22, 1932 2 Claims.

This invention relates to glass grinding apparatus and has for itsobject means for forcing the abrasive towards the glass.

In glass grinding apparatus in which the grinding tool does not operateon the upper surface of horizontally placed fiat glass, as, for example,in apparatus in which the two surfaces of flat glass are groundsimultaneously, it has been found dimcult to maintain a supply ofabrasive, (comld monly sand and water) between the grinding surface andthe glass.

The grinding tool commonly used is a rotating disc provided with nogs orblocks of cast iron generally of rectangular form.

According to the present invention, each block has its leading faceinclined to the radius forwardly (in reference to the direction ofrotation) and outwardly, and also forwardly away from its operativesurface.

In the accompanying drawing:- Figure l is a plan [(partly broken away)of the operative surface of'a grinding tool according to the invention;

Figure 2 is a section thereof along the line 22 of Figure 1;

Figure 3 is a section along the crooked line 3-3 of Figure 1;

Figure 4 is a diagrammatic plan showing a single block; and

Figure 5 is a perspective view of Figure 1, looking down at an angle ofto the horizontal. The circular disc 1, with operative surface 2,commonly made in cast iron, is attached to the flange 3 of the tool. Thedisc 1 has a central aperture 4, surrounding which, is an annularchannel 5 with an approximately central web 11. Outside this channel 5,is the operative surface 2, which is divided into three rings by twocircular grooves 6. Of these three rings, the two inner ones are dividedup into blocks or-nogs 7 by grooves 8, while the outer ring has similargrooves 8 which do not, however, extend tothe periphery of the disc 1.

Assuming the disc 1 to rotate in the direction of the arrows shown inFigures l and 5,. the

grooves 8 are inclmed to the radii outwardy and forwardly in thedirection of rotation, as seen in Figurel." 'rFur-ther, the grooves areinclined to the surface oi' gthe disc, as shown in Figure 3, the

inclination being"3forwardly away from the operative surface, that is tosay, forwardly and downwardly in the tool shown.

Abrasive (commonly sand and water) is supplied through the hole 9 to thecentral aperture 4 65 and passes below the inner wall 10 of the channel5. Apertures 12 in the web 11 (only one such aperture is represented inFigure 1) permit the abrasive to rise into the upper part of the channel5, and from this the abrasive is forced outwardly along the grooves 8 bycentrifugal force.

By reason of the inclination of the grooves, the abrasive, in movingoutwardly under centrifugal force, tends to move upwardly towards theoperative surface. Referring to Figure 4, which shows a single block,with operative surface 2 and inclined surface 13 formed by the inclinedgroove 8, imagine a pxrticle of abrasive C. The centre of the tool beingat O, the particle is acted on by centrifugal force in the direction ofCD, and by gravity downwards from the paper. If the particle were ableto move in the direction CD, it would be accelerated in movingoutwardly, because its velocity would increase with its radius. If itmoved along the bottom of the groove, in the direction CE, its motionwould be still further accelerated. The particle can be accelerated inits circular motion only by pressure exerted on it by the surface 13and, since this is inclined, the pressure has an upward verticalcomponent, which, by suitable choice of inclinations and 30 speeds, canbe sufficient to overcome the downward force of gravity.

The particle, in fact, will tend to move along a path such as CF, inwhich its motion is not accelerated, and this path brings it from thebot- 35 tom of the groove to the operative surface.

The essential feature of the invention therefore lies in each block '7having its leading face 13 inclined to the radius outwardly andforwardly and forwardly away from its operative surface. The leadingfaces 13 are shown shaded in Figure 5.

The tool described above, gives blocks of this form and can beconveniently manufactured from a disc of cast iron. The tool, however,may be constructed by bolting blocks on to a fiat disc. The circulargrooves 6 do not form an essential part of the invention, but it ispreferable for the sake of better distribution, that the inclinedgrooves 8 should be connected by cross grooves.

The circular grooves 6 or other cross grooves may be so inclined, thatthe inner face of each block is inclined inwardly away from theoperative surface, so that the centrifugal force acting on the abrasiveagainst the inner faces, tends to move it towards the operative surface.The abrasive is not, however, so readily engaged between the operativesurface and the glass, as when it is brought to the surface at theleading faces of the blocks. 1

The inclination of the leading faces of the blocks to the radii, ispreferably made greater, the greater the distance of the block from thecentre.

The invention is particularly applicable to glass grinding apparatusoperating on the underside of the glass, when gravity tends to keep theabrasive the leading face of each block being inclined both to theradius and to the operative surface, the inclination to the radius beingsuch that as the radius increases the face extends from the radius inthe direction of rotation and the-inclination to the operative planebeing such that portions away from the operative surface are furtherforward than portions nearer to the operative surface.

2. In glass grinding apparatus a grinding runner having its operativesurface formed into blocks by grooves in a disc adapted to lead theabrasive outwardly and cross-connecting grooves, the first mentionedgrooves being inclined to the radii forwardly and outwardly and alsoinclined to the operative surface in a direction forwardly away from thesurface.

FREDERIC BARNES WALDRON.

